System and method for administering digital certificate checking

ABSTRACT

Systems and methods for handling electronic messages. An electronic message that is associated with a digital certificate is to be processed. A decision whether to check the validity of the digital certificate is based upon digital certificate checking criterion. An IT administrator may provide to one or more devices configuration data that establishes the digital certificate checking criterion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/974,944, filed Dec. 21, 2010, which is a continuation of U.S.application Ser. No. 11/065,946, filed Feb. 25, 2005 (now U.S. Pat. No.7,882,348, issued Feb. 1, 2011), which claims priority from U.S.Application No. 60/566,789, filed Apr. 30, 2004, the entireties of whichare incorporated herein by reference.

BACKGROUND

1. Technical Field

The present invention relates generally to the field of communications,and in particular to handling digital certificates on mobile wirelesscommunications devices.

2. Description of the Related Art

In S/MIME and similar systems where digital certificates are used toestablish identity, there are mechanisms in place to check the validityof the certificates. As an illustration, the OCSP (Online CertificateStatus Protocol) process could be used to check the validity of acertificate every time an electronic message (e.g., e-mail message) issent. This allows a person to determine if the certificate for acommunications partner was valid at the time that a message was sentfrom them or to ensure that it is still valid when a message is to besent to them.

However, checking certificates every time or too often would most likelyresult in slowdowns, lost battery life and higher data costs—especiallyin the case when dealing with a group of people or when a conversationis proceeding with messages going back and forth (e.g., checking eachtime for each recipient is not wireless friendly).

SUMMARY

In accordance with the teachings disclosed herein, methods and systemsare provided for handling an electronic message. As an example of asystem and method, an electronic message that is associated with adigital certificate is to be processed. A digital certificate checkingmodule determines whether to check the validity of the digitalcertificate based upon the length of time since the last time thedigital certificate was checked.

As another example, a system and method may include an IT administratorproviding configuration data to one or more devices that establisheswhat period of time should expire before validity of a digitalcertificate should be checked.

As will be appreciated, the systems and methods disclosed herein arecapable of other and different embodiments, and its several details arecapable of modifications in various respects. Accordingly, the drawingsand description set forth below are to be regarded as illustrative innature and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overview of an example communication system in which awireless communication device may be used.

FIG. 2 is a block diagram of a further example communication systemincluding multiple networks and multiple mobile communication devices.

FIG. 3 is a block diagram depicting a system for checking digitalcertificates.

FIG. 4 is a block diagram depicting a data store for use in checkingdigital certificates.

FIGS. 5 and 6 depict an operational scenario for checking a digitalcertificate.

FIGS. 7-9 are blocks diagrams wherein digital certificate-related datais provided by an IT administrator.

FIG. 10 is a block depicting a message recipient performing acertificate status check determination.

FIG. 11 is a block diagram of an example mobile device.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overview of an example communication system in which awireless communication device may be used. One skilled in the art willappreciate that there may be hundreds of different topologies, but thesystem shown in FIG. 1 helps demonstrate the operation of the encodedmessage processing systems and methods described in the presentapplication. There may also be many message senders and recipients. Thesimple system shown in FIG. 1 is for illustrative purposes only, andshows perhaps the most prevalent Internet e-mail environment wheresecurity is not generally used.

FIG. 1 shows an e-mail sender 10, the Internet 20, a message serversystem 40, a wireless gateway 85, wireless infrastructure 90, a wirelessnetwork 105 and a mobile communication device 100.

An e-mail sender system 10 may, for example, be connected to an ISP(Internet Service Provider) on which a user of the system 10 has anaccount, located within a company, possibly connected to a local areanetwork (LAN), and connected to the Internet 20, or connected to theInternet 20 through a large ASP (application service provider) such asAmerica Online (AOL). Those skilled in the art will appreciate that thesystems shown in FIG. 1 may instead be connected to a wide area network(WAN) other than the Internet, although e-mail transfers are commonlyaccomplished through Internet-connected arrangements as shown in FIG. 1.

The message server 40 may be implemented, for example, on a networkcomputer within the firewall of a corporation, a computer within an ISPor ASP system or the like, and acts as the main interface for e-mailexchange over the Internet 20. Although other messaging systems mightnot require a message server system 40, a mobile device 100 configuredfor receiving and possibly sending e-mail will normally be associatedwith an account on a message server. Perhaps the two most common messageservers are Microsoft Exchange™ and Lotus Domino™. These products areoften used in conjunction with Internet mail routers that route anddeliver mail. These intermediate components are not shown in FIG. 1, asthey do not directly play a role in the secure message processingdescribed below. Message servers such as server 40 typically extendbeyond just e-mail sending and receiving; they also include dynamicdatabase storage engines that have predefined database formats for datalike calendars, to-do lists, task lists, e-mail and documentation.

The wireless gateway 85 and infrastructure 90 provide a link between theInternet 20 and wireless network 105. The wireless infrastructure 90determines the most likely network for locating a given user and tracksthe user as they roam between countries or networks. A message is thendelivered to the mobile device 100 via wireless transmission, typicallyat a radio frequency (RF), from a base station in the wireless network105 to the mobile device 100. The particular network 105 may bevirtually any wireless network over which messages may be exchanged witha mobile communication device.

As shown in FIG. 1, a composed e-mail message 15 is sent by the e-mailsender 10, located somewhere on the Internet 20. This message 15 isnormally fully in the clear and uses traditional Simple Mail TransferProtocol (SMTP), RFC822 headers and Multipurpose Internet Mail Extension(MIME) body parts to define the format of the mail message. Thesetechniques are all well known to those skilled in the art. The message15 arrives at the message server 40 and is normally stored in a messagestore. Most known messaging systems support a so-called “pull” messageaccess scheme, wherein the mobile device 100 must request that storedmessages be forwarded by the message server to the mobile device 100.Some systems provide for automatic routing of such messages which areaddressed using a specific e-mail address associated with the mobiledevice 100. As described in further detail below, messages addressed toa message server account associated with a host system such as a homecomputer or office computer which belongs to the user of a mobile device100 are redirected from the message server 40 to the mobile device 100as they are received.

Regardless of the specific mechanism controlling the forwarding ofmessages to the mobile device 100, the message 15, or possibly atranslated or reformatted version thereof, is sent to the wirelessgateway 85. The wireless infrastructure 90 includes a series ofconnections to wireless network 105. These connections could beIntegrated Services Digital Network (ISDN), Frame Relay or T1connections using the TCP/IP protocol used throughout the Internet. Asused herein, the term “wireless network” is intended to include threedifferent types of networks, those being (1) data-centric wirelessnetworks, (2) voice-centric wireless networks and (3) dual-mode networksthat can support both voice and data communications over the samephysical base stations. Combined dual-mode networks include, but are notlimited to, (1) Code Division Multiple Access (CDMA) networks, (2) theGroupe Special Mobile or the Global System for Mobile Communications(GSM) and the General Packet Radio Service (GPRS) networks, and (3)future third-generation (3G) networks like Enhanced Data-rates forGlobal Evolution (EDGE) and Universal Mobile Telecommunications Systems(UMTS). Some older examples of data-centric network include the Mobitex™Radio Network and the DataTAC™ Radio Network. Examples of oldervoice-centric data networks include Personal Communication Systems (PCS)networks like GSM, and TDMA systems.

FIG. 2 is a block diagram of a further example communication systemincluding multiple networks and multiple mobile communication devices.The system of FIG. 2 is substantially similar to the FIG. 1 system, butincludes a host system 30, a redirection program 45, a mobile devicecradle 65, a wireless virtual private network (VPN) router 75, anadditional wireless network 110 and multiple mobile communicationdevices 100. As described above in conjunction with FIG. 1, FIG. 2represents an overview of a sample network topology. Although theencoded message processing systems and methods described herein may beapplied to networks having many different topologies, the network ofFIG. 2 is useful in understanding an automatic e-mail redirection systemmentioned briefly above.

The central host system 30 will typically be a corporate office or otherLAN, but may instead be a home office computer or some other privatesystem where mail messages are being exchanged. Within the host system30 is the message server 40, running on some computer within thefirewall of the host system, that acts as the main interface for thehost system to exchange e-mail with the Internet 20. In the system ofFIG. 2, the redirection program 45 enables redirection of data itemsfrom the server 40 to a mobile communication device 100. Although theredirection program 45 is shown to reside on the same machine as themessage server 40 for ease of presentation, there is no requirement thatit must reside on the message server. The redirection program 45 and themessage server 40 are designed to co-operate and interact to allow thepushing of information to mobile devices 100. In this installation, theredirection program 45 takes confidential and non-confidential corporateinformation for a specific user and redirects it out through thecorporate firewall to mobile devices 100. A more detailed description ofthe redirection software 45 may be found in the commonly assigned U.S.Pat. No. 6,219,694 (“the '694 patent”), entitled “System and Method forPushing Information From A Host System To A Mobile Data CommunicationDevice Having A Shared Electronic Address”, and issued to the assigneeof the instant application on Apr. 17, 2001 which is hereby incorporatedinto the present application by reference. This push technique may use awireless friendly encoding, compression and encryption technique todeliver all information to a mobile device, thus effectively extendingthe security firewall to include each mobile device 100 associated withthe host system 30.

As shown in FIG. 2, there may be many alternative paths for gettinginformation to the mobile device 100. One method for loading informationonto the mobile device 100 is through a port designated 50, using adevice cradle 65. This method tends to be useful for bulk informationupdates often performed at initialization of a mobile device 100 withthe host system 30 or a computer 35 within the system 30. The other mainmethod for data exchange is over-the-air using wireless networks todeliver the information. As shown in FIG. 2, this may be accomplishedthrough a wireless VPN router 75 or through a traditional Internetconnection 95 to a wireless gateway 85 and a wireless infrastructure 90,as described above. The concept of a wireless VPN router 75 is new inthe wireless industry and implies that a VPN connection could beestablished directly through a specific wireless network 110 to a mobiledevice 100. The possibility of using a wireless VPN router 75 has onlyrecently been available and could be used when the new Internet Protocol(IP) Version 6 (IPV6) arrives into IP-based wireless networks. This newprotocol will provide enough IP addresses to dedicate an IP address toevery mobile device 100 and thus make it possible to push information toa mobile device 100 at any time. A principal advantage of using thiswireless VPN router 75 is that it could be an off-the-shelf VPNcomponent, thus it would not require a separate wireless gateway 85 andwireless infrastructure 90 to be used. A VPN connection could be aTransmission Control Protocol (TCP)/IP or User Datagram Protocol(UDP)/IP connection to deliver the messages directly to the mobiledevice 100. If a wireless VPN 75 is not available then a link 95 to theInternet 20 is the most common connection mechanism available and hasbeen described above.

In the automatic redirection system of FIG. 2, a composed e-mail message15 leaving the e-mail sender 10 arrives at the message server 40 and isredirected by the redirection program 45 to the mobile device 100. Asthis redirection takes place the message 15 is re-enveloped, asindicated at 80, and a possibly proprietary compression and encryptionalgorithm can then be applied to the original message 15. In this way,messages being read on the mobile device 100 are no less secure than ifthey were read on a desktop workstation such as 35 within the firewall.All messages exchanged between the redirection program 45 and the mobiledevice 100 may use this message repackaging technique. Another goal ofthis outer envelope is to maintain the addressing information of theoriginal message except the sender's and the receiver's address. Thisallows reply messages to reach the appropriate destination, and alsoallows the “from” field to reflect the mobile user's desktop address.Using the user's e-mail address from the mobile device 100 allows thereceived message to appear as though the message originated from theuser's desktop system 35 rather than the mobile device 100.

With reference back to the port 50 and cradle 65 connectivity to themobile device 100, this connection path offers many advantages forenabling one-time data exchange of large items. For those skilled in theart of personal digital assistants (PDAs) and synchronization, the mostcommon data exchanged over this link is Personal Information Management(PIM) data 55. When exchanged for the first time this data tends to belarge in quantity, bulky in nature and requires a large bandwidth to getloaded onto the mobile device 100 where it can be used on the road. Thisserial link may also be used for other purposes, including setting up aprivate security key 111 such as an S/MIME or PGP specific private key,the Certificate (Cert) of the user and their Certificate RevocationLists (CRLs) 60. The private key can be exchanged so that the desktop 35and mobile device 100 share one personality and one method for accessingall mail. The Cert and CRLs are normally exchanged over such a linkbecause they represent a large amount of the data that is required bythe device for S/MIME, PGP and other public key security methods.

FIG. 3 shows at 140 a system for checking digital certificates 154 thatare associated with message recipients. In the example of FIG. 3, amessage sender 150 wishes to send an e-mail message 151 to one or moremessage recipients 170. The sender 150 uses data from a recipient'sdigital certificate 154 in order to encode the message 151 beforesending it to a recipient 170.

The digital certificate 154 may include many different types ofinformation for use in encoding, such as the certificate holder's name,serial number, expiration dates, a copy of the certificate holder'spublic key, etc. Digital certificates can conform to the X.509 standard(or another type of standard), and can be kept in registries accessibleover a network 160 from certificate authorities (CAs) so that anauthenticating user (e.g., sender 150) can obtain other users' digitalcertificates.

The system 140 establishes a balance between security assurance andconvenience, by checking digital certificates 154 on a pre-determinedperiodicity. That is, once an assurance time period 155 is establishedthat balances security concerns with performance considerations, thesystem 140 checks the digital certificate status if the last checkoccurred outside of the assurance period 155. As an illustration, if anassurance period of four hours is established and if the status check ofdigital certificate 154 occurred more than four hours ago, then a newcheck of the digital certificate 154 is performed; else a check of thedigital certificate 154 is not performed.

If the certificate status check fails (e.g., the certificate has beenrevoked), the system 140 can alert the user of the mobile device 100 andallow them to search for a new certificate or take other correctiveaction. The system 140 can also be configured such that the user cansend to that revoked certificate recipient if still desired.

It should be understood that an assurance period 155 can be selectedbased upon many considerations, such as based upon a recognition that aCRL does not typically change in small time frames. A typicalinstallation might see their CRLs updated about every four hours andhence that periodicity can serve as a basis to specify the time lag onthe mobile device 100 between checks. If needed, an assurance period 155could be set to cause a check with every message sent or received, orwith every connection.

The mobile device 100 can be configured in different ways in order touse an assurance period 155 to check digital certificates 154. Themessage sender 150 on the mobile device 100 can access a digitalcertificate checking module or routine 152. The checking routine 152determines whether to check validity of a digital certificate 154 basedupon certificate checking criterion information. The certificatechecking criterion information can be stored in a data store 158 and beused by the checking routine 152 to determine whether certificatevalidity checking should occur. As an illustration, checking criterioninformation includes temporal information such as what the assuranceperiod 155 is and what was the last checking time 156 for a digitalcertificate 154.

As shown in FIG. 4, data store 158 can be configured to contain manydifferent types of information, such as multiple different assuranceperiods (180, 182, 184). Different assurance periods (180, 182, 184) canbe used depending upon the situation at hand. For example, a firstassurance period 180 can be selected from the checking data store 158 bythe checking routine 152 when dealing with a digital certificate from aparticular certificate authority; a second assurance period 182 may beused when dealing with a digital certificate issued from a differentcertificate authority. It should be understood that different assuranceperiods may be used because of other factors, such as but not limitedto, trust status, encryption versus signing of the message, level ofencryption, priority of the message, importance of the message, etc.

FIG. 5 depicts an operational scenario for checking a digitalcertificate. Indicator 200 indicates that a sender is preparing to senda message that has to be encrypted. Decision step 202 examines whetherdigital certificates of the message recipient(s) need to be validatedbefore encrypting the message. If no validation is needed, then themessage is encoded and sent at step 206. However, if one or more of thedigital certificates need to be validated, then such certificates arevalidated at step 204.

Decision step 208 examines whether a message should be sent. A messagemight not be sent to a recipient if the recipient's certificate cannotbe validated or fails the validation process (e.g., because it hasexpired). If the message is not to be sent, then processing for thisoperational scenario ends at end block 210. If the message is to besent, then the message is encoded and sent at step 206. Processing endsat end block 210.

FIG. 6 illustrates an operational scenario for determining whether acertificate needs to be validated based upon temporal considerations.Indicator 250 indicates that processing begins at step 252. Step 252determines the last time that a particular certificate was checked. Ifthe last time of the check is within a predetermined threshold (e.g., anassurance period) as determined at decision step 254, then an indicationis returned at 256 that the certificate does not have to be validated.However, if decision step 254 determines that the last time of the checkis outside of the predetermined threshold, then an indication isreturned at 258 that the certificate needs to be validated. It should beunderstood that similar to the other processing flows described herein,the steps and the order of the steps in the flowchart described hereinmay be altered, modified and/or augmented and still achieve the desiredoutcome.

Another operational scenario is shown in FIG. 7, wherein an IT(information technology) administrator 270 specifies the assuranceperiod(s) 272 (e.g., time limits before checking messages) to one ormore mobile devices (e.g., device 100). The assurance period(s) 272 areprovided to the mobile device 100 over the network 160 (or other dataconnection mechanism) to update the checking data store 158. The mobiledevice 100 can be pre-programmed with an assurance period which can beupdated by the IT administrator 270 or can have the initial assuranceperiod provided by an IT administrator 270. A system can be configuredto also allow a user to set a more aggressive/secure assurance period.For example, if an IT administrator has designated a check of every fourhours, a user can set on her mobile device a more secure setting, suchas every three hours.

This provides, among other things, companies with the capability tocustomize assurance periods to suit their needs. Also, an ITadministrator 270 can provide the same settings to all mobile devices ofthe company, thereby ensuring that company mobile devices adhere to aconsistent IT policy.

An IT policy can be enforced upon mobile devices in many ways. FIGS. 8and 9 describe an example of this and is further described in thefollowing commonly assigned United States patent application which ishereby incorporated by reference: “System And Method Of Owner Control OfElectronic Devices” (Ser. No. 10/732,132 filed on Dec. 10, 2003). Theexample illustrates how a user of the mobile device can be preventedfrom altering or erasing assurance periods specified by an ITadministrator.

FIG. 8 is a block diagram illustrating a system of inserting ownerinformation and owner control information (e.g., assurance period(s))onto an electronic mobile device. The system in FIG. 8 includes anelectronic device 310, an owner information insertion point 320, and anowner control information insertion point 330. The owner informationinsertion point 320 is alternatively referred to as a branding point,while the owner control insertion point 330 is alternatively referred toas a control point. An owner information store 312, an owner controlinformation store 314, and an interface/connector 316 are provided inthe electronic device 310. The owner information insertion point 320includes an owner information source 324 and an interface/connector 322.The owner control information insertion point 330 similarly includes anowner control information source 334 and an interface/connector 332.

The owner information store 312 stores information, such as an ownername or other identification information, for example, which identifiesan owner of the electronic device 310. The owner control informationstore 314 stores information that is used to control the operation ofthe electronic device 310. Owner control information may, for example,be specified in an authorization record that lists software applicationsauthorized to be installed and executed on the electronic device 310(e.g., such information can include that a digital certificate checkingmodule 152 must be used and with a particular assurance period). Theowner information source 324 and the owner control information source334 could be local memory devices, communication modules through whichremote memory devices storing owner information and owner controlinformation are accessible, or possibly user interfaces through whichowner information and owner control information are entered.

The interface/connector 322 is compatible with the interface/connector316 to establish a communication link between the owner informationinsertion point 320 and the electronic device 310, to thereby enableowner information to be transferred to the electronic device 310 fromthe owner information source 324. The interface/connector 332 similarlyenables transfer of owner control information from the owner controlinformation source 334 onto the electronic device 310 via acommunication link established between the interface/connectors 332 and316. The interface/connectors 316, 322, and 332 may establish wiredcommunication links, where the interface/connectors are serial ports,for example, or wireless communication links such as infrared linkswhere the interface/connectors are infrared modules, or wirelesscommunication networks. Owner information and owner control informationtransferred to a device are respectively inserted or stored in the ownerinformation store 312 and the owner control information store 314.

The owner control insertion point 320 is associated with an owner of theelectronic device 310. Where the electronic device 310 is provided to auser (e.g., operator of the device) by an employer, for example, theowner control insertion point 320 may be a computer system or devicecontrolled by a corporate computer system administrator or ITdepartment. The electronic device 310 is “branded” with ownerinformation by establishing a communication link between the ownerinformation insertion point 320 and the electronic device 310 throughthe interface/connectors 322 and 316 and then inserting ownerinformation into the owner information store 312. Unless otherwisedesired, once owner information has been inserted onto the mobile device310, then only the owner or a party authorized by the owner may be ableto change the owner information or insert or change owner controlinformation on the electronic device 310.

Because insertion of owner control information onto the electronicdevice 310 is restricted once owner information has been inserted, theowner control information insertion point 330 need not necessarily becontrolled by the owner of the electronic device 310. When the ownermaintains control over the owner control information insertion point330, the insertion points 320 and 330 may be implemented in the samecomputer system or device and share the same interface/connector.However, separate insertion points 320 and 330 as shown in FIG. 8 allowan owner of the electronic device to delegate owner control informationinsertion to a trusted entity. If owner control information insertion iscontrolled using digital signatures, for example, an owner first brandsthe electronic device 310 and provides the electronic device 310 anddigitally signed owner control information to a user. In this case, theowner control information insertion point 330 may be the user's computersystem, which is then used to insert the digitally signed owner controlinformation onto the electronic device 310.

In most implementations, the owner information insertion point 320 andthe owner control information control point 330 include the same type ofinterface/connectors 322 and 332, compatible with theinterface/connector 316 in the electronic device 310. However, theelectronic device 310 may alternatively include multipleinterface/connectors, such that different types of interface/connectorsmay be implemented at an owner information insertion point 320 and anowner control information insertion point 330. Although only a singleowner control information insertion point 320 and owner controlinformation insertion point 330 are shown in FIG. 8, a completeinsertion system may include more than one of each type of insertionpoint. In a large company, for example, corporate computer systemadministrators may be authorized to perform owner information insertionoperations from administrator computer systems, or from any corporatecomputer system from which administrative functions can be accessed,thereby providing multiple owner information insertion points 320.Similarly, when an owner allows users to insert digitally signed ownercontrol information onto electronic devices, each user's computer systemmay be used as an owner control information insertion point 330.

FIG. 9 is a block diagram of an electronic device in which a system andmethod of owner application control can be implemented. In FIG. 9, theelectronic device is a mobile device 30 adapted to operate within awireless network. Also shown in FIG. 9 is an insertion tool 64 used toinsert owner information onto the mobile device 30.

It should be apparent to those skilled in the art that only thecomponents involved in an owner control system are shown in FIG. 9. Amobile device typically includes further components in addition to thoseshown in FIG. 9. Also, the mobile device 30 is an illustrative exampleof an electronic device for which an owner may wish to enforce some sortof usage policy. An owner may also wish to control the usage of othertypes of electronic devices, such as mobile telephones, laptop computersand PDAs, for example.

As shown in FIG. 9, a mobile device 430 comprises a memory 432, aprocessor 440, an application loader 442, an insertion module 444, auser interface (UI) 446, a wireless transceiver 448, and aninterface/connector 450. The memory 432 may include a softwareapplications store 434, an owner information store 436, an authorizationrecord store 438, as well as possibly other data stores associated withother device systems in addition to those shown in FIG. 9, such as achecking data store to store assurance period(s).

The memory 432 is a writable store such as a RAM or Flash memory intowhich other device components may write data. However, write and eraseaccess to the software application store 434, the owner informationstore 436, and the authorization record store 438 is preferablyrestricted, but need not be in all implementations. For example, a userof the mobile device 430 may be able to retrieve data from the stores434, 436, and 438, but write and erase operations for these stores arecontrolled, as described below. The software application store 434includes software applications that have been installed on the mobiledevice 430, and may include, for example, a digital certificate checkingapplication, an electronic messaging application, a personal informationmanagement (PIM) application, games, as well as other applications. Theowner information store 436 stores information such as an owner name orother identification, data integrity and source authenticationinformation, such as a digital signature public key associated with adigital signature private key of the owner. Owner control information,in which an owner of the mobile device 430 specifies usage permissionsand restrictions for the mobile device 430, is stored in anauthorization record in the authorization record store 438. Suchauthorization records can include one or more of the aforementionedrequired, allowed and/or excluded application lists.

The processor 440 is connected to the wireless transceiver 448 and thusenables the mobile device 430 for communications via a wireless network.The application loader 442 and insertion module 444, described infurther detail below, are connected to the interface/connector 450 toallow communication with the insertion tool 464, through theco-operating interface/connector 452.

The UI 446 includes one or more UI components, such as a keyboard orkeypad, a display, or other components which accept inputs from orprovide outputs to a user of the mobile device 430. Although shown as asingle block in FIG. 9, it should be apparent that a mobile device 430typically includes more than one UI, and the UI 446 is thereforeintended to represent one or more user interfaces.

The insertion tool 464 includes an owner information store 460 and aninterface/connector 452 through which information is exchanged with themobile device 430, and thus represents an owner information insertionpoint 320 (FIG. 8). As described above, an owner information insertionpoint such as the insertion tool 464 may be controlled by an owner of anelectronic device. Therefore, the insertion tool 464 is, for example,implemented on an administrator computer system used by an authorizedadministrator to enable services for or otherwise configure the mobiledevice 430. Because networked computer systems can typically be used byany user, the insertion tool 464 may instead be accessible to anycomputer system in a corporate network, dependent upon the particularuser that is currently “logged on” the computer system.

The owner information store 460 stores owner information to be insertedonto the mobile device 430, and may be implemented, for example, on alocal memory component such as a RAM chip, a flash memory device, or ahard disk drive. When the insertion tool 464 is implemented in anetworked computer system or other network-connected device, the ownerinformation store 460 may be a remote memory system such as a fileserver that is accessible to the insertion tool 464 through a networkconnection. The owner information store 460 may instead incorporate amemory reader such as a smart card reader, a memory card reader, afloppy disk drive, or a CD or DVD drive, for example.

Information is transferred between the insertion tool 464 and the mobiledevice 430 via a communication link established between theinterface/connectors 450 and 452. The interface/connectors 450 and 452could be any of a plurality of compatible data transfer components,including, for example, optical data transfer interfaces such asInfrared Data Association (IrDA) ports, other short-range wirelesscommunications interfaces, or wired interfaces such as serial orUniversal Serial Bus (USB) ports and connections. Known short-rangewireless communications interfaces include, for example, “Bluetooth”modules and 802.11 modules according to the Bluetooth or 802.11specifications, respectively. It will be apparent to those skilled inthe art that Bluetooth and 802.11 denote sets of specifications,available from the Institute of Electrical and Electronics Engineers(IEEE), relating to wireless LANs and wireless personal area networks,respectively. Therefore, a communication link between the insertion tool464 and the mobile device 430 may be a wireless connection or a physicalwired connection.

Because communications between the insertion tool 464 and the mobiledevice 430 need not necessarily be accomplished using a physicalconnection, references to connecting a mobile device to an insertiontool include establishing communications through either physicalconnections or wireless transfer schemes. Thus, the mobile device 430could be connected to the insertion tool 464 by connecting serial portson the mobile device 430 and the insertion tool 464, by positioning themobile device 430 such that an optical port thereof is in a line ofsight of a similar port of the insertion tool 464, or by connecting orarranging the mobile device 430 and the insertion tool 464 in some othermanner so that data may be exchanged. The particular operations involvedin establishing communications between a mobile device and an insertiontool are dependent upon the types of interfaces and/or connectorsavailable in both the mobile device and the insertion tool.

Owner branding of the mobile device 430 may be facilitated by insertingowner information onto the mobile device 430 using the insertion tool464 before the mobile device 430 is operable by a user. This may beaccomplished, for example, by pre-loading owner information before themobile device 430 is provided to the user by the owner, or before themobile device 430 is configured for use. In the former example, theowner maintains physical control of the mobile device 430 until ownerinformation has been loaded, whereas in the latter example, the user haspossession of the mobile device 430 but preferably is unable to make useof the device until it is configured by, or at least under the controlof, the owner.

Pre-loading of owner information onto the mobile device 430 is performedusing the insertion tool 464. As described briefly above, the insertiontool 464 may be a computer system associated with an a owner systemadministrator, or a computer system which may be used by a mobile deviceuser or administrator. Depending upon the owner information pre-loadingscheme, the insertion tool 464 is operated by a mobile device user or anadministrator.

When the mobile device 430 has been connected to the insertion tool 464,owner information is retrieved from the owner information store 460 andtransferred to the mobile device 430 through the interface/connectors452 and 450, and passed to the insertion module 444 on the mobile device430, which stores the owner information to the owner information store436 in the memory 432.

Although the insertion module 444 is shown in FIG. 9 as being connectedto the interface/connector 450, this module is normally implemented as asoftware module or application that is executed by the processor 440. Assuch, data transfers to and from the interface/connector 450 mayactually be accomplished by routing data through the processor 440 tothe interface/connector 450. In this case, the processor 440 may beinstructed by the insertion tool 464 to start the insertion module 444before the owner information is transferred to the mobile device 430.Alternatively, the processor 440 may be configured to start theinsertion module 444 whenever owner information is received. Theinsertion tool 464 may similarly be a software module or applicationthat is executed by a processor (not shown) in a computer system ordevice on which the insertion tool 464 operates.

The owner information that is pre-loaded onto the mobile device 430 mayinclude data integrity and/or source authentication information, such asa cryptographic system like a digital signature public key whichcorresponds to a digital signature private key used by the owner todigitally sign information before it is transferred to the mobile device430. Pre-loading of the data integrity and/or source authenticationinformation enables greater security of owner control operations. Ownerinformation may also include, for example, a name or other identifierassociated with the owner of the mobile device 430.

In an owner control scheme in which digital signatures are used toverify data integrity and authenticate a source of data, when theowner's digital signature public key has been inserted into the ownerinformation store 436 on the mobile device 430, owner controlinformation, which specifies permissions and/or restrictions for themobile device 430, is inserted onto the mobile device 430. Although anowner information insertion point, insertion tool 464, is shown in FIG.9, it will be apparent from FIG. 8 and the above description that ownercontrol information is usually inserted onto an electronic device afterthe device has been branded by inserting owner information onto thedevice. An owner control information insertion tool (not shown)configured for use with the mobile device 430 is similar to theinsertion tool 464, including an owner control information store and aninterface/connector compatible with the interface/connector 450. Ownercontrol information is inserted onto the mobile device 430 and stored inthe form of an authorization record in the authorization record store438. In an authorization record, an owner of the mobile device 430specifies a list of software applications that a user is authorized toinstall on the mobile device 430, as well as possibly a list of requiredsoftware applications that must be installed on the mobile device 430.

In order to prevent a user from inserting false owner controlinformation to thereby circumvent owner control, owner controlinformation is preferably digitally signed using the owner's digitalsignature private key before being transferred to the mobile device 430.The insertion module 444 is preferably configured to verify the digitalsignature before the owner control information is stored on the mobiledevice 430. If digital signature verification fails, then the ownercontrol information is not stored on the mobile device 430.

Digital signature schemes generally involve some sort of transformationof digitally signed information to provide for checking the integrity ofthe information and authentication of a source of the signedinformation. For example, according to one known digital signaturetechnique, a digest of information to be digitally signed is firstgenerated using a non-reversible digest algorithm or transformation.Known digest algorithms include Secure Hashing Algorithm 1 (SHA-1) andMessage-Digest algorithm 5 (MD5). Other digest techniques that produce aunique digest for each unique input may also be used. The digest is thenfurther transformed using a digital signature private key and asignature algorithm to generate a digital signature. In digitalsignature verification, a digital signature public key corresponding tothe private key is used.

In the context of owner control and owner control information, insertionof the owner's digital signature public key on a mobile device 430 aspart of the owner information provides for digital signature-basedsecurity of owner control information. If all owner control informationis digitally signed before transfer to the mobile device 430, then theinsertion module 444 can verify that owner control information hasactually been signed using the owner's digital signature private key,known only to the owner, and that the owner control information has notbeen changed since it was signed. In this manner, only owner controlinformation that originates with the owner of a mobile device 430 isstored to and used on the mobile device 430.

Owner control information is obtained by an owner control informationinsertion tool from an owner control information store, which may be aremote data store accessible to the insertion tool, a local store, orsome form of memory reader, as described above. Owner controlinformation is established based on a set of software applications orfunctions (e.g., digital certificate checking routine) or data (e.g.,assurance period(s)) that the owner wishes to authorize on an electronicdevice. Such owner control information could then be digitally signed bya secure computer system or software component to which onlyadministrators have access, using the owner's digital signature privatekey. In this case, signed owner control information is then stored at alocation that is accessible to administrator computer systems andpossibly other computer systems, and retrieved by an owner controlinformation insertion tool as required. The owner control informationinsertion tool then transfers the signed owner control information tothe mobile device 430. Depending upon how often owner controlinformation changes or is expected to change, the signed owner controlinformation may be further distributed to each computer system in anetwork in order to provide local access to signed owner controlinformation. When new owner control information is generated and signed,the signed new owner control information preferably replaces allexisting copies of the owner control information, as described infurther detail below. Wide distribution of owner control informationprovides easier access to the owner control information, whereas sharedremote storage of owner control information requires fewer updates whennew owner control information is established.

It is also possible to support digital signature generation for ownercontrol information on an owner control information insertion tool.However, in the present example, this would require that the ownercontrol information insertion tool has access to the owner's digitalsignature private key. Unless otherwise desired, digital signing ofowner control information only by secure computer systems or componentsis generally preferred in that it limits the number of computer systemsthat can access the owner's digital signature private key.

When signed owner control information is transferred to the insertionmodule 444, digital signature verification operations are performed. Ifthe digital signature is verified, then the owner control information isstored on the mobile device 430 in the authorization record store 438.Otherwise, the owner control information is not stored. In the event ofa digital signature verification failure, an error or like indicationmay be output to a user on a UI 446 such as a display, an error messagemay be returned to the owner control information insertion tool, and anindication of the failure may also be output to a user of the ownercontrol information insertion tool. When owner control informationinsertion fails, retry or other error processing operations may beperformed on the owner control information insertion tool, the mobiledevice 430, or both.

A first owner information insertion operation for any mobile device 430is preferably either performed or authorized by an administrator, inorder to ensure that accurate owner control information is inserted ontothe mobile device 430. This prevents a user from circumventing ownercontrol by inserting a digital signature public key other than theowner's digital signature public key onto the mobile device 430.

When owner control information changes, where an owner wishes to expandor further restrict the use of an electronic device, for example, anyexisting owner control information preferably should be replaced. Asdescribed above, new owner control information is preferably digitallysigned, and the signed new owner control information is distributed toone or more locations from which it is retrieved for insertion ontoelectronic devices.

Any of several mechanisms for subsequent distribution of signed newowner control information to electronic devices are possible. When newowner control information is distributed to each owner controlinformation insertion tool, the insertion tool may be configured todetect receipt of new owner control information, and to transfer the newowner control information to the mobile device 430 the next time themobile device 430 is connected to the owner control informationinsertion tool. As described above, an owner control informationinsertion point 330 (FIG. 8), such as an owner control informationinsertion tool, may be controlled by a user of an electronic device.Many modern electronic devices are configured to be synchronized withcomputer systems. In such systems, this type of owner controlinformation distribution may be supported by implementing an ownerinformation control insertion tool in a user's computer system. Newowner control information is then transferred to the electronic devicethe next time the electronic device is synchronized with the computersystem.

Initial storage of owner control information, as well as replacement ofexisting owner control information, is in this example thereby dependentupon verification of a digital signature by the insertion module 444.Those skilled in the art will appreciate that other checks may also beperformed before existing information is replaced. In order to preventreplay attacks, in which old owner control information is received bythe electronic device, owner control information preferably includesversion information. Existing owner control information is replaced onlywhere received owner control information is newer than the existingowner control information. Generally, newer owner control informationhas a higher version number.

Although owner information is inserted onto the mobile device 430 usingthe insertion tool 464 as described above, changes to existing ownerinformation, such as when the owner's digital signature private/publickey pair is changed, may alternatively be updated on the mobile device430 using digital signature techniques. To this end, the insertion tool464 may include other types of communication modules (not shown), suchas a wireless transceiver or network connector, for example, that areless secure than the interface/connector 452. In that case, any suchupdates are dependent upon verification of a digital signature using adigital signature public key in existing owner information.

The foregoing description relates primarily to writing owner informationand owner control information to memory on an electronic device such asthe mobile device 430. However, an owner may also wish to erase ownerinformation and owner control information, without replacing existinginformation with new information. In this case, because information isnot being written to memory on a device, no signed owner information orowner control information would be sent to the device. Instead, an erasecommand or request may be sent to the device. Erasure may be a furtherfunction supported by the insertion module 444.

If owner information is to be erased from the owner information store436, then an erase command or request is digitally signed and sent tothe insertion module 444. As with new owner information or owner controlinformation, a signed command or request could be sent to the mobiledevice 430 through either the interface/connector 450 or the wirelesstransceiver 448. The insertion module 444, using the owner's digitalsignature public key, executes the command or completes the request onlyif a digital signature is verified. Otherwise, the command or requestmay be ignored, and an error or failure indication may be displayed to auser on a UI 446 on the mobile device 430, returned to a sending systemor device that sent the command or request, or both. Further error orfailure processing routines may then be performed at the sending systemor device.

Since owner information includes the owner's digital signature publickey in a signature-based owner control scheme, erasure of ownerinformation may be tightly controlled. For example, only owner systemadministrators may be authorized to send erase commands or requests.Sending of signed commands or requests to the mobile device 430 istherefore preferably restricted to administrator computer systems oraccounts, an owner information insertion tool, or an owner-controllederasure tool. For example, an insertion tool such as the insertion tool464 could be adapted to erase existing owner information from the mobiledevice 430 by providing an erase command generator or store which isalso coupled to the interface/connector 452. Alternatively, ownerinformation erasure could be accomplished using a specialized,owner-controlled erasure tool incorporating such an erase commandgenerator or store and an interface to the mobile device 430. Erasure ofowner control information is preferably controlled in a similar manner.

Where an owner control system is configured to support erasure andpossibly other owner information and owner control informationmanagement functions, access to the owner's digital signature privatekey is preferably restricted in order to control the information,requests, and commands that can be digitally signed and sent to anelectronic device. The digital signature private key or digitalsignature generation functions may be accessible only to specificcomputer systems or administrator login accounts, for example.

As shown in FIG. 9, other systems on the mobile device 430 have accessto the memory 432. Preferably, no device system should be able toinsert, change, or erase owner information or owner control informationwithout submitting properly signed information or commands. Any datastores, such as the owner information store 436 and the authorizationrecord store 438, that store owner information or owner controlinformation are therefore preferably located in protected memory areas.Preferably, only the insertion module 444 has write and erase access tothese stores, such that digital signature-based control of insertion anderasure of owner information and owner control information ismaintained. Other device systems have read only access to ownerinformation and owner control information. In one possibleimplementation, any systems or components through which the memory 432is accessible are configured to allow memory read operations from anylocations in the memory 432, but deny any write or erase operations tomemory locations storing owner information or owner control informationunless the operations originate with or are authorized by the insertionmodule 444. In an alternative implementation, a memory manager (notshown) is provided to manage all memory access operations. Such a memorymanager is configured to direct any write or erase operations involvingowner information or owner control information stores to the insertionmodule 444 for digital signature checking and authorization beforecompleting the operations. Owner information and owner controlinformation may thereby be read by other device systems, but preferablymay only be inserted, changed, or erased when a digital signature isverified.

It should be appreciated that the above public key digital signatureoperations are intended only as an illustrative example. Other digitalsignature schemes, or other data integrity checking and sourceauthentication schemes, may instead be used to verify the integrity andsource of owner control information or commands. Further, theauthentication and security described herein above are preferably usedto transfer the owner application control information; however, varioussystems and methods of owner application control need not useauthentication and/or secure transmission in order to achieve thedesired owner application control as described herein.

In the mobile device 430, owner control information is included in anauthorization record that is stored in the authorization record store438. An authorization record specifies particular software applicationsthat are authorized for installation on the mobile device 430, and mayalso specify required software applications (e.g., digital validitychecking module 152) and data (e.g., assurance period(s)) that must beinstalled and used on the mobile device 430. Such an authorizationrecord provides an electronic device owner with relatively tight controlof how a user makes use of the mobile device 430, since only authorizedsoftware applications and/or data can be loaded onto the device.

For authorized or required applications, some systems can provide a morefine grained control within the authorization record(s). In suchsystems, the owner can provide more specific controls on the operationsthat installed application can perform. Such controls can be specifiedon an individual application basis, or in some cases by groups ofapplications. Such operation controls can determine whether anapplication can connect to external resources, and if so, the channelsthat may be used for such connections, can communicate with otherapplications executing on the device and/or can access part or all oflocal memory on the device.

Software application loading operations are enabled on the mobile device430 by the application loader 442. As described above in regard to theinsertion module 444, although the application loader 442 is shown asbeing connected to the interface/connector 450, information may actuallybe exchanged between the application loader 442 and theinterface/connector 450 or the wireless transceiver 448 through theprocessor 440.

Like owner information and owner control information, softwareapplications may be received by the mobile device 430 via theinterface/connector 450 or the wireless transceiver 448. One possiblesource of software applications configured for operation on the mobiledevice 430 is a user's computer system equipped with aninterface/connector compatible with the interface/connector 450. Whenthe computer system is connected to a corporate LAN, for example,software applications provided by a corporate owner of the mobile device430 may be retrieved from a file server on the LAN or other store on theLAN, and transferred to the mobile device. A computer system may also orinstead obtain software applications for the mobile device 430 from alocal store, or other sources, such as Internet-based sources, withwhich the computer system may communicate.

The application loader 442 is preferably configured to determine whetherowner control information is stored on the mobile device 430 whenever asoftware application is received. If no owner control information ispresent on the mobile device 430, then no owner controls have beenestablished for the mobile device 430, and the software application isinstalled. Alternatively, the application loader 442 could consult aremote server for an owner control information update prior toattempting the installation. Software application installation typicallyinvolves such operations as storing a received application file to thesoftware application store 434 in the memory 432, extracting files forstorage to the software application store 434, or possibly executing aninstallation program or utility. If owner control information issubsequently inserted onto the mobile device 430, existing softwareapplications are preferably checked by either the application loader 442or the insertion module 444 to ensure that all software applicationsresident on the mobile device 430 are authorized software applications.Any software applications that have not been authorized are erased fromthe mobile device 430 or otherwise rendered inoperable.

In some circumstances, owner information may have been inserted onto anelectronic device, but owner control information has yet to be inserted.In order to prevent loading of a software application onto the mobiledevice 430 that subsequently inserted owner control information does notauthorize, the mobile device 430 may be substantially disabled,permitting only a limited subset of device functions to be executed,until owner control information is inserted. Alternatively, theapplication loader 442 may be configured to determine whether ownerinformation is present on the mobile device 430 when a softwareapplication is received. Where owner information is found, indicatingthat owner control information will be established and used for themobile device 430, the application loader 442 then determines whetherowner control information has been inserted. In the event that ownerinformation but not owner control information is found, the applicationloader 442 does not load the received software application. Errorprocessing operations may then be performed, such as purging thereceived software application from any temporary memory location inwhich it was stored when received, and, if memory resources on themobile device 430 permit, storing the received software application onthe mobile device 430 in such a way that it is not executable. Anysoftware applications stored in this manner are then processed by theapplication loader 442 when owner control information is inserted ontothe mobile device 430. Although software applications are stored on themobile device 430 in this embodiment, they would not be usable untilowner control information is inserted onto the mobile device 430, and itis confirmed that the software applications are authorized forinstallation. The amount of memory space made available for suchsoftware applications may occupy is preferably limited, so thatavailable memory space will not be depleted by storing unchecked andpossibly unauthorized software applications.

When the application loader 442 determines that owner controlinformation has been inserted onto the mobile device 430, theapplication loader 442 then determines whether the received softwareapplication is authorized for installation on the mobile device 430. Ifthe owner control information includes an authorized softwareapplication list, the application loader 442 searches the list todetermine whether the received software application is one of theauthorized software applications. An authorized software applicationlist preferably includes information that uniquely identifies theauthorized software applications, such as a hash of the softwareapplication source code or executable code, for example. Because asoftware application developer is free to choose a file name for anysoftware application, file names may not provide a reliableauthorization check. However, if an owner generates a hash of eachauthorized software application and includes the hash in the ownercontrol information that is inserted onto the mobile device 430, thenonly particular versions of authorized software applications can beinstalled on the mobile device 430. The application loader 442 generatesa hash of any received software application, and installs the softwareapplication only if the generated hash matches a hash in the ownercontrol information. In order to support different hashing algorithms ondifferent electronic devices, a device owner generates more than onehash of each software application and includes each hash in the ownercontrol information inserted onto each owned electronic device. Anelectronic device may then use any of a number of different hashingalgorithms to generate a hash of a received software application. Ofcourse, other unique transformations than hashes could also be used togenerate owner control information and to determine whether receivedsoftware applications are authorized for installation.

Owner control information may also include a required softwareapplication list that uniquely identifies software applications that theowner of an electronic device establishes as mandatory. A requiredsoftware application list allows an owner to ensure that every ownedelectronic device supports certain core functions, such as electronicmessaging and secure communications, for example. Software applicationsin a required software application list may be uniquely identified byone or more hashes, as described above in the context of authorizedapplications. The processor 440, application loader 442, insertionmodule 444, or a further device component or system is configured toperiodically check to ensure that each required software application ispresent on the mobile device 430, and that a hash of each requiredsoftware application matches a hash in the required software applicationlist. Where a required software application is not present on the deviceor its hash does not match a hash in the required software applicationlist, which would occur when a software application has been changed,the mobile device 430, or at least some of its functions, can berendered unusable. Alternatively, the mobile device 430 can download andinstall missing or corrupted applications transparently to the user ofthe device; after successful installation of all required programs, thedevice is restored to operability.

The systems and methods disclosed herein are presented only by way ofexample and are not meant to limit the scope of the invention. Othervariations of the systems and methods described above will be apparentto those skilled in the art and as such are considered to be within thescope of the invention. For example, it should be understood that thesystems and methods disclosed herein may be used whenever validation ofa digital certificate is used such as certificate status checks usingOCSP. FIG. 10 depicts another situation where a certificate status checkdetermination is performed by a recipient 520 of a message from sender500 received over network 510. A digital certificate checking routine522 determines whether the digital certificate associated with thesender 500 needs to be validated before processing the message. Thechecking routine 522 can base its decision upon an assurance period 524and the time that the digital certificate was last checked. Othersituations where digital certificate checking may be used include butare not limited to: negotiating a secure connection (SSL/TLS); or othercertificate-based secure communication schemes (e.g., PGP).

As another example, the systems and methods disclosed herein may be usedwith many different computers and devices, such as a wireless mobilecommunications device shown in FIG. 11. With reference to FIG. 11, themobile device 100 is a dual-mode mobile device and includes atransceiver 611, a microprocessor 638, a display 622, non-volatilememory 624, random access memory (RAM) 626, one or more auxiliaryinput/output (I/O) devices 628, a serial port 630, a keyboard 632, aspeaker 634, a microphone 636, a short-range wireless communicationssub-system 640, and other device sub-systems 642.

The transceiver 611 includes a receiver 612, a transmitter 614, antennas616 and 618, one or more local oscillators 613, and a digital signalprocessor (DSP) 620. The antennas 616 and 618 may be antenna elements ofa multiple-element antenna, and are preferably embedded antennas.However, the systems and methods described herein are in no wayrestricted to a particular type of antenna, or even to wirelesscommunication devices.

The mobile device 100 is preferably a two-way communication devicehaving voice and data communication capabilities. Thus, for example, themobile device 100 may communicate over a voice network, such as any ofthe analog or digital cellular networks, and may also communicate over adata network. The voice and data networks are depicted in FIG. 11 by thecommunication tower 619. These voice and data networks may be separatecommunication networks using separate infrastructure, such as basestations, network controllers, etc., or they may be integrated into asingle wireless network.

The transceiver 611 is used to communicate with the network 619, andincludes the receiver 612, the transmitter 614, the one or more localoscillators 613 and the DSP 620. The DSP 620 is used to send and receivesignals to and from the transceivers 616 and 618, and also providescontrol information to the receiver 612 and the transmitter 614. If thevoice and data communications occur at a single frequency, orclosely-spaced sets of frequencies, then a single local oscillator 613may be used in conjunction with the receiver 612 and the transmitter614. Alternatively, if different frequencies are utilized for voicecommunications versus data communications for example, then a pluralityof local oscillators 613 can be used to generate a plurality offrequencies corresponding to the voice and data networks 619.Information, which includes both voice and data information, iscommunicated to and from the transceiver 611 via a link between the DSP620 and the microprocessor 638.

The detailed design of the transceiver 611, such as frequency band,component selection, power level, etc., will be dependent upon thecommunication network 619 in which the mobile device 100 is intended tooperate. For example, a mobile device 100 intended to operate in a NorthAmerican market may include a transceiver 611 designed to operate withany of a variety of voice communication networks, such as the Mobitex orDataTAC mobile data communication networks, AMPS, TDMA, CDMA, PCS, etc.,whereas a mobile device 100 intended for use in Europe may be configuredto operate with the GPRS data communication network and the GSM voicecommunication network. Other types of data and voice networks, bothseparate and integrated, may also be utilized with a mobile device 100.

Depending upon the type of network or networks 619, the accessrequirements for the mobile device 100 may also vary. For example, inthe Mobitex and DataTAC data networks, mobile devices are registered onthe network using a unique identification number associated with eachmobile device. In GPRS data networks, however, network access isassociated with a subscriber or user of a mobile device. A GPRS devicetypically requires a subscriber identity module (“SIM”), which isrequired in order to operate a mobile device on a GPRS network. Local ornon-network communication functions (if any) may be operable, withoutthe SIM device, but a mobile device will be unable to carry out anyfunctions involving communications over the data network 619, other thanany legally required operations, such as ‘911’ emergency calling.

After any required network registration or activation procedures havebeen completed, the mobile device 100 may the send and receivecommunication signals, including both voice and data signals, over thenetworks 619. Signals received by the antenna 616 from the communicationnetwork 619 are routed to the receiver 612, which provides for signalamplification, frequency down conversion, filtering, channel selection,etc., and may also provide analog to digital conversion. Analog todigital conversion of the received signal allows more complexcommunication functions, such as digital demodulation and decoding to beperformed using the DSP 620. In a similar manner, signals to betransmitted to the network 619 are processed, including modulation andencoding, for example, by the DSP 620 and are then provided to thetransmitter 614 for digital to analog conversion, frequency upconversion, filtering, amplification and transmission to thecommunication network 619 via the antenna 618.

In addition to processing the communication signals, the DSP 620 alsoprovides for transceiver control. For example, the gain levels appliedto communication signals in the receiver 612 and the transmitter 614 maybe adaptively controlled through automatic gain control algorithmsimplemented in the DSP 620. Other transceiver control algorithms couldalso be implemented in the DSP 620 in order to provide moresophisticated control of the transceiver 611.

The microprocessor 638 preferably manages and controls the overalloperation of the mobile device 100. Many types of microprocessors ormicrocontrollers could be used here, or, alternatively, a single DSP 620could be used to carry out the functions of the microprocessor 638.Low-level communication functions, including at least data and voicecommunications, are performed through the DSP 620 in the transceiver611. Other, high-level communication applications, such as a voicecommunication application 624A, and a data communication application624B may be stored in the non-volatile memory 624 for execution by themicroprocessor 638. For example, the voice communication module 624A mayprovide a high-level user interface operable to transmit and receivevoice calls between the mobile device 100 and a plurality of other voiceor dual-mode devices via the network 619. Similarly, the datacommunication module 624B may provide a high-level user interfaceoperable for sending and receiving data, such as e-mail messages, files,organizer information, short text messages, etc., between the mobiledevice 100 and a plurality of other data devices via the networks 619.The microprocessor 638 also interacts with other device subsystems, suchas the display 622, the RAM 626, the auxiliary input/output (I/O)subsystems 628, the serial port 630, the keyboard 632, the speaker 634,the microphone 636, the short-range communications subsystem 640 and anyother device subsystems generally designated as 642.

Some of the subsystems shown in FIG. 11 perform communication-relatedfunctions, whereas other subsystems may provide “resident” or on-devicefunctions. Notably, some subsystems, such as the keyboard 632 and thedisplay 622 may be used for both communication-related functions, suchas entering a text message for transmission over a data communicationnetwork, and device-resident functions such as a calculator or task listor other PDA type functions.

Operating system software used by the microprocessor 638 is preferablystored in a persistent store such as non-volatile memory 624. Thenon-volatile memory 624 may be implemented, for example, as a Flashmemory component, or as battery backed-up RAM. In addition to theoperating system, which controls low-level functions of the mobiledevice 610, the non-volatile memory 624 includes a plurality of softwaremodules 624A-624N that can be executed by the microprocessor 638 (and/orthe DSP 620), including a voice communication module 624A, a datacommunication module 624B, and a plurality of other operational modules624N for carrying out a plurality of other functions. These modules areexecuted by the microprocessor 638 and provide a high-level interfacebetween a user and the mobile device 100. This interface typicallyincludes a graphical component provided through the display 622, and aninput/output component provided through the auxiliary I/O 628, keyboard632, speaker 634, and microphone 636. The operating system, specificdevice applications or modules, or parts thereof, may be temporarilyloaded into a volatile store, such as RAM 626 for faster operation.Moreover, received communication signals may also be temporarily storedto RAM 626, before permanently writing them to a file system located ina persistent store such as the Flash memory 624.

An exemplary application module 624N that may be loaded onto the mobiledevice 100 is a personal information manager (PIM) application providingPDA functionality, such as calendar events, appointments, and taskitems. This module 624N may also interact with the voice communicationmodule 624A for managing phone calls, voice mails, etc., and may alsointeract with the data communication module for managing e-mailcommunications and other data transmissions. Alternatively, all of thefunctionality of the voice communication module 624A and the datacommunication module 624B may be integrated into the PIM module.

The non-volatile memory 624 preferably also provides a file system tofacilitate storage of PIM data items on the device. The PIM applicationpreferably includes the ability to send and receive data items, eitherby itself, or in conjunction with the voice and data communicationmodules 624A, 624B, via the wireless networks 619. The PIM data itemsare preferably seamlessly integrated, synchronized and updated, via thewireless networks 619, with a corresponding set of data items stored orassociated with a host computer system, thereby creating a mirroredsystem for data items associated with a particular user.

Context objects representing at least partially decoded data items, aswell as fully decoded data items, are preferably stored on the mobiledevice 100 in a volatile and non-persistent store such as the RAM 626.Such information may instead be stored in the non-volatile memory 624,for example, when storage intervals are relatively short, such that theinformation is removed from memory soon after it is stored. However,storage of this information in the RAM 626 or another volatile andnon-persistent store is preferred, in order to ensure that theinformation is erased from memory when the mobile device 100 losespower. This prevents an unauthorized party from obtaining any storeddecoded or partially decoded information by removing a memory chip fromthe mobile device 100, for example.

The mobile device 100 may be manually synchronized with a host system byplacing the device 100 in an interface cradle, which couples the serialport 630 of the mobile device 100 to the serial port of a computersystem or device. The serial port 630 may also be used to enable a userto set preferences through an external device or software application,or to download other application modules 624N for installation. Thiswired download path may be used to load an encryption key onto thedevice, which is a more secure method than exchanging encryptioninformation via the wireless network 619. Interfaces for other wireddownload paths may be provided in the mobile device 100, in addition toor instead of the serial port 630. For example, a USB port would providean interface to a similarly equipped personal computer.

Additional application modules 624N may be loaded onto the mobile device100 through the networks 619, through an auxiliary I/O subsystem 628,through the serial port 630, through the short-range communicationssubsystem 640, or through any other suitable subsystem 642, andinstalled by a user in the non-volatile memory 624 or RAM 626. Suchflexibility in application installation increases the functionality ofthe mobile device 100 and may provide enhanced on-device functions,communication-related functions, or both. For example, securecommunication applications may enable electronic commerce functions andother such financial transactions to be performed using the mobiledevice 100.

When the mobile device 100 is operating in a data communication mode, areceived signal, such as a text message or a web page download, isprocessed by the transceiver module 611 and provided to themicroprocessor 638, which preferably further processes the receivedsignal in multiple stages as described above, for eventual output to thedisplay 622, or, alternatively, to an auxiliary I/O device 628. A userof mobile device 100 may also compose data items, such as e-mailmessages, using the keyboard 632, which is preferably a completealphanumeric keyboard laid out in the QWERTY style, although otherstyles of complete alphanumeric keyboards such as the known DVORAK stylemay also be used. User input to the mobile device 100 is furtherenhanced with a plurality of auxiliary I/O devices 628, which mayinclude a thumbwheel input device, a touchpad, a variety of switches, arocker input switch, etc. The composed data items input by the user maythen be transmitted over the communication networks 619 via thetransceiver module 611.

When the mobile device 100 is operating in a voice communication mode,the overall operation of the mobile device is substantially similar tothe data mode, except that received signals are preferably be output tothe speaker 634 and voice signals for transmission are generated by amicrophone 636. Alternative voice or audio I/O subsystems, such as avoice message recording subsystem, may also be implemented on the mobiledevice 100. Although voice or audio signal output is preferablyaccomplished primarily through the speaker 634, the display 622 may alsobe used to provide an indication of the identity of a calling party, theduration of a voice call, or other voice call related information. Forexample, the microprocessor 638, in conjunction with the voicecommunication module and the operating system software, may detect thecaller identification information of an incoming voice call and displayit on the display 622.

A short-range communications subsystem 640 is also included in themobile device 100. The subsystem 640 may include an infrared device andassociated circuits and components, or a short-range RF communicationmodule such as a Bluetooth™ module or an 802.11 module, for example, toprovide for communication with similarly-enabled systems and devices.Those skilled in the art will appreciate that “Bluetooth” and “802.11”refer to sets of specifications, available from the Institute ofElectrical and Electronics Engineers, relating to wireless personal areanetworks and wireless local area networks, respectively.

The invention claimed is:
 1. A method, comprising: receiving a pluralityof time periods at a mobile communication device, each time period ofthe plurality of time periods defining a periodicity for checkingvalidity of a digital certificate; storing the plurality of time periodsat the mobile communication device; after receiving and storing theplurality of time periods, the mobile communication device: receiving adigital certificate for a recipient; selecting, in dependence on one ormore factors, a time period for use with the digital certificate fromthe plurality of time periods; and validating the digital certificatewhen a last time since a validity of the digital certificate was checkedis not within the selected time period.
 2. The method of claim 1,wherein the selecting and the validating occurs upon an indication thata message is to be encrypted using the digital certificate at the mobilecommunication device.
 3. The method of claim 1, wherein the plurality oftime periods are received from a different source than the digitalcertificate.
 4. The method of claim 1, wherein the plurality of timeperiods are received over a wireless network from an administratorsystem.
 5. The method of claim 1, wherein the one or more factorscomprise an identity of a certificate authority issuing the digitalcertificate, such that a first time period is selected for a firstcertificate authority and a second time period is selected for a secondcertificate authority.
 6. The method of claim 1, wherein a message is tobe encrypted at the mobile communication device using the digitalcertificate, and the one or more factors comprise a level of encryptionto be applied to the message.
 7. The method of claim 1, wherein amessage is to be encrypted at the mobile communication device using thedigital certificate, and the one or more factors comprise a priority orimportance of the message.
 8. The method of claim 1, wherein theplurality of time periods are stored separately from the digitalcertificate.
 9. A mobile communication device, comprising: at least onecommunication subsystem; at least one memory component; and at least oneprocessor in communication with the at least one communication subsystemand the at least one memory component, the at least one processor beingconfigured to enable: receiving a plurality of time periods using the atleast one communication subsystem, each time period of the plurality oftime periods defining a periodicity for checking validity of a digitalcertificate; storing the plurality of time periods in the at least onememory component; after receiving and storing the plurality of timeperiods: receiving a digital certificate for a recipient; selecting, independence on one or more factors, a time period for use with thedigital certificate from the plurality of time periods; and validatingthe digital certificate when a last time since a validity of the digitalcertificate was checked is not within the selected time period.
 10. Themobile communication device of claim 9, wherein the selecting and thevalidating occurs upon an indication that a message is to be encryptedusing the digital certificate at the mobile communication device. 11.The mobile communication device of claim 9, wherein the plurality oftime periods are received from a different source than the digitalcertificate.
 12. The mobile communication device of claim 9, wherein theplurality of time periods are received over a wireless network from anadministrator system.
 13. The mobile communication device of claim 9,wherein the one or more factors comprise an identity of a certificateauthority issuing the digital certificate, such that a first time periodis selected for a first certificate authority and a second time periodis selected for a second certificate authority.
 14. The mobilecommunication device of claim 9, wherein a message is to be encrypted atthe mobile communication device using the digital certificate, and theone or more factors comprise a level of encryption to be applied to themessage.
 15. The mobile communication device of claim 9, wherein amessage is to be encrypted at the mobile communication device using thedigital certificate, and the one or more factors comprise a priority orimportance of the message.
 16. The mobile communication device of claim9, wherein the plurality of time periods are stored separately from thedigital certificate.
 17. A non-transitory electronic device-readablemedium bearing code which, when executed by at least one processor of anelectronic device, causes the electronic device to implement the methodof: receiving a plurality of time periods, each time period of theplurality of time periods defining a periodicity for checking validityof a digital certificate; storing the plurality of time periods; afterreceiving and storing the plurality of time periods: receiving a digitalcertificate for a recipient; selecting, in dependence on one or morefactors, a time period for use with the digital certificate from theplurality of time periods; and validating the digital certificate when alast time since a validity of the digital certificate was checked is notwithin the selected time period.
 18. The non-transitory electronicdevice-readable medium of claim 17, wherein the plurality of timeperiods are received from a different source than the digitalcertificate.
 19. The non-transitory electronic device-readable medium ofclaim 17, wherein the one or more factors comprise an identity of acertificate authority issuing the digital certificate, such that a firsttime period is selected for a first certificate authority and a secondtime period is selected for a second certificate authority.
 20. Thenon-transitory electronic device-readable medium of claim 17, whereinthe plurality of time periods are stored separately from the digitalcertificate.